Process for producing cast iron castings



. duce sound dense A typical one is A.

Patented Martin 1945 raooass ron monome os s'r r'noN- AS'I'INGS ,1.

Oliver Smaller, New Rochelle, min, and Herbert i A. Reece, ClevelandHelghtnOhlo No Drawing. Application i943, I

Serial No; 499,242

Our invention relates to the process of melting steel scrap, cast ironand pig iron in such quantitles as to control the solidity penetratingpower during the process of solidification so as to prothrough allsections and having related physical iron castings uniformly solid 0 Theremedyiior these defects is sometimes sought in changing the chemicalcomposition, or

n the addition; of special metals such as nickel, chrome, molybdenum, orcopper, or a combination of these smetala but even so, trouble withleakers and open texture and mechanical weakproperties, and to thecasting produced by the process. 1

In the production of foundry castings it is a desideratum to obtaincastings having physical.

' properties and matrix structures best suited to the type of service inwhich the castings are to be used. The structures of castings are theimportant factors in the ability of the castings to meet the partic--ular requirements of the use to which the castings are but.

There have been many approaches to the problem of obtaining desiredphysical properties and matrix structures in iron castings, some ofwhich are successful to a limited degree. However,- all of the knownmethods have a lack of uniformity and inherent limitations on thecertainties of results.

In the ordinary method of making gray cast iron or semi-steel castings,certain mixtures of pig iron, scrap and/or steel are used to obtain inphysical properties and matrix ness on change of section may still beevident. In other words, the properties of the test bar do not tellwhether the casting itself will be solid or acceptable, nor does anacceptable chemical speciflcationassure a sound casting.

To eliminate such 7 production of castings that are sound and solid inall their secti ns, the applicants have discovered that chemicalanalysis of itself is of secondary-consideration and is not a definitecri-- terion of either t e physical pro erties or of the solidity of anycasting, but rather that the physical constitution ofthe iron, i. e..the arrangement of thestructural components, one with another,

is the determining factor. Our invention deals 1 with physicalconstitutionalcontrol and enables the finished casting a certain.predetermined chemical composition, total carbon, silicon, manganese,sulphur and phosphorus. By adjusting this analysis, the resultingproduct has certain physical characteristics which identifies it asconforming to some recognized physical property specification.

S. 'I'. M. specifications A126-30:

Tensile strength minimum, 30,000 lbs. p. s. 1.

Transverse load minimum, 3,300 lbs. on a 1.2 'inch bar broken over 120inch centers with a minimum deflection of .12 inch.

Chemical analysis, maximum .12 sulphur and maximum .75 phosphorus. I

The result of this method of operation is to produce an iron which meetsthe physical property specification requirements on the standard A. F.A. arbitration bar or the A. S. T. M. test bar, yet the castingsproduced may still be rejected because of porosity or, shrink defectswhen twin or more sections conioin; or the metal itself may lackcloseness of grain and fail under pressure test or on machinng maydisplay structural weakness as is commonly revealed on machining theteeth of a gear blank, for example.

us to manufacture an iron to some predetermined austenite content at;the,..solldus, whose latent heat value of carbides on passing from theliquid to the solid condition is held within'specific limits. It is anobjectof our invention to provide an accuratemethod of producingcastings having a relation of structural components to assure accuratelycontrolled physical properties, solidity, and matrix structure.

Another object is the elimination of defects common .to conjoiningsections of iron castings. Another object is the provision foraccurately forecasting definite properties in relation to sec- I tionofcasting.

- relation with the car Another object is to control the soliditypenetrating power of a given cast iron.

Another object isthe provision for controlling the latent heat values ofan iron on solidification.

Another object is to adjust the rate of recarbonization for castings ofpredetermined requirements.

- Another object is a two-stepprocess of making cast irons, comprisingasa -first step selecting a mixture of raw materials-which when meltedwill yield a structuralconstitution having a direct the quantity of freecementite present, and as a second step decomposing the free cementiteso that the final structure consists of free carbon in a wholly pearlitematrix. I

Another object is to provide for the relation of carbide balance in aniron of given physical constitution to a given section of casting. v

defects and to assure the idelbalance as measured by 2 asrnou Anotherobject is to provide tor the relation of Iron No. 2 carbide balance tosection to eilect better ma- Mixture: Pounds chinability in combinationwith the maximum iron 200 hysical properties-in any given section.silvery pig Another object is to govern the structural con- Spiegel Istitution through the nature of the raw material Steel scrap 400 makingup the furnace charge. t e D----------------------- 400 Another objectis to provide for and control the Analysis latent heat value 0! themolten iron.- I

Anotherobject is the provision for inhibiting 1 Total carbon theformation oi. free ferrite which may other- 511mm wise form under theprocesses utilized in ordl- Manganese. nary pracucm Phosphorus .15

Another object of our invention is the provisulphur 992 slon 0! an ironcasting in the as cast" state 15 w these were poured into test'bars ofvaryhaving a solidity penetrating power such as gives sizes molded f othe same, pattern, the fol, castings M W dimension lowing test resultswere obtained: Other objects and a fuller understanding or no N ourinvention will become apparent from the following description and theclaims herein.

How the process is applied in practice to asgi a??? sure the productionofcastings oi uniform structure and properties, is illustrated by thefollow- L613 49 m ing examples: .894 800 No. 1 assumes an iron made froma mixture 2:, jig comprising '70 per cent steel scrap, 20 per cent .52554,800 returned scrap, and 10 per cent pig iron, and

No. 2 assumes an iron made up approximately 01 40 per cent steel scrap,40 per cent returned 1301' 2 scrap, and 20 per cent pi iron. so

The chemical analysis oi the resulting iron Bar Tensile from each may ormay not be exactly the same. This is not of prime importance. In eachcase, the mixture charged in the cupola is calculated 1% 31% to a givenspecific heat value at the solidus tem- 3.3 .804 100 perature ofapproximately 2150 F. which on 3%; 3:238 cooling to room temperature.will result in a .405 48,800 given amount of free cementite, which isthe first t p 0! 0111 M 8 From these results it will be observed thechem- Having obtained the correct amount of tree 40 ical analysis is notthe prime controlling factor m t te. the second step or our pr ess c oieither the constitution or hysical properties sists of decomposing theexcess cementite to v of t finished cast1ng assure that y p fll'llticmatrix resul s, con- When Iron No. 1 was poured into a 4-inch or t m noree c te o free r i e. and thicker casting, it was foundto be uniformlysolid yie d uni ormly lid, h mogeneous castings of and exhibited thesame graphite structure from maximum physical properties with freemachinthe edge to the center. ing qualities. When Iron No. 2 was pouredinto castings 1- AS Pointed Out hereihbefolehave found inch or even2-inches thick, it was found to give t the chemical ys i not of itself auniformly solid castings but when it was poured definite criterion ofeither e physical p p into 4-inch thick castings, it was found that thet 1 f e o y f cflstlng- This y he graphite structure was larger in thecenter than exp ai ed wit r fe e t the followins testsin the outer zonesand also that in the center Two mixtures of irons of pp a y t e some orthe casting, there was a atch of open texture chem analysis. p htemperat etc., material which had a low strength. when Iron were meltedin the same cupola. wi the Same No. 1 was poured into the same casting,that is, typ f c a under similar conditions of a 4-inch thick casting,substantially the same control. tensile strength was uniformly obtainedthrough- The mixtures and the results'ale given below! out all sections,whereas in the case of Iron No. 2 when poured in the 4-inch thick castinthe IRON 1 tensile strength in the center of the section fell to lessthan half of that indicated by the 1.2 inch Mi Pounds A. s. '1'. M. testbar.

Pi ir This is what is meant by solidity penetrating v y P 8 power; IronNo. 1 was solid all the way through; Spiesel 5 Iron No. 2 was not. St 8m) Iron No. 1 may be seen to have the property Returned scraP---- ofsolidifying uniformly throughout all sections of reasonably proportionedcastings. while Iron No. Analysis 4 2 is only capable of yieldinguniiormly solid cast 70 lugs to a thickness or approximately 2 inches. Ttal arb n 3.13 Ordinary common gray iron such as is used in sili on 1.58the average foundry, comprising a mixture or 40 Mang ese .63 per centpig iron and 60 per cent scrap, would Phosphorus .14 only give a solidcasting to a depth approximating Sulphur .091 II one inch.

wnstitution ofrtl e melt.

' carcass "For. many-years, this problemand its iclution has bailied thefound industry. Some claim a charcoal pig iron, melted high graphiticpig iron because of its improved fluidity results in a graphitenucleation which will correct the defect. vOthers'endeavor to change thecomposition of the iron by adding or the use of specially"slow.

alloys or by using mechanical chillers or casting in specially designedmolds, etc.--all of which at the best, are but pailiatives and have manydellnite limitations in their application to commercial manufacture orcasting including dependability of product, cgnsistency of result andprice.

Since shrinks arevoids left between the dendrites after the eutecticliquidihas to make up for the liquid-shrinkage. in adjacent but coolersections, the finer-the dendritic pattern and the smaller theinterstices between the crystals, the less likely the draining of theeutectic from one area to another. Instead of then having. as is socommon with ordinary gray cast iron, a comparatively large poroussection which in castings of heavy or varying sections means drained outsteel 35% return scrap Silicon and manganese Y Bricf uettes to giveacalculated chemical content 01 i .l

mechanical weakness. andleakage if used under pressure, we have a largenumber ,of minute voids uniformly distributed but not interconnected.and

"which permit uniform solidification conditions throughout the wholemass.

This might be illustrated bypouring a casting of wedge form. The Knifeedge. cools instantaneously while the heavy see-tion cools much moreslowly, and the resultis a varying texture in'ithe casting, from theknife edge to the center, and. often a shrink spot'in'the center. Thewedgeshaped casting has an acute angle, defining a knife edge, rangingfrom approximately to 30 degrees. If this wedge is poured with IronNo.1, the

depth oi penetration oi' 'the cementitic carbide is much greater than inthe case 01' gray 'cast iron, and thecenter of the mass is free'fromstructural weakness.

If, however, the casting were poured with a high carbide value, thechances are it would not be machina-ble and may display hard white edgesand free cementite. However, by decom posing this cem'entite to graphiteand pearlite such that the ignal structure consists oi free graphite orcarbon in a substantially wholly pearlitlc niatrizn 'we reproduce aniron whose chilling value is'the same. as the gray iron above. yet atthe same time produces a much more dense and refined structure, andwhich on pouring into the casting, is uniformly solid throughout. g

- In our invention the constitution" of the metal is established accorddesign of the casting The establishment of the constitution of the metalmay be explained by comparing two mixtures designated"A and BJ' eachcontaining the same elements of charge and resulting in the sameanalysis but having a diilferent recarbonization rate which aflect the A75% steel return scrap. Silieon and manganese Briquettes to give aPhosphorus -r; .12

;to:"th'e thickness and calculated chemical convalue of 1.96% which isobtained by subtracting 1.12 total carbon in the mixture prior tomelting from 3.08 total carbon for the mixture after melting, while the3" mixture has a jrecarbonization valueoi' 1.55% which is obtained bysub-.

tracting 1.53 total carbon-for the mixture "before carbon for themixture melting from 3-.08 total after melting. The constitution, of the"'A" iron measured in a wedge test of standard size was;

while the constitution of the 3" iron meastest was The wedge testcomprises the pouring of a casting of a pre-determined length and ofwedge form 1 in cross-section with an acute ang ured by the samestandard wedge e of approximately 20to 30degrees. of several sizes,namely, one-half inch basewith approximately 28.5 acute angle,three-fourths inch base with approximately 26.75 acute angle.

one inch 'base with approximately 25 acute angle.

. and two inch base withapproximately 23.5 acute "can discern that theangle. After the wedge casting is poured and The wedges may be cooled,"it is broken in two so that the carbide I balance may be observed. Uponobservation one white appearance while the remaining base portion has agray appearance- In the white por-p tion, the carbon is, generally incombined form, and in the gray portion erally in graphite form; Thewhite portion is unmachinable. The width across the face of a wedge usedto make the test.

across the face .of the wedge at the line of the the wedge at the lineof demarcation between i 1 the white and the gray portion is a measureof the constitution of the iron. Thus, in the example of the "A" ironabove, the wedge measuredacute angle portion has athejfree carbon is geninch across the face thereof at the line of,

demarcation. The wedge siges are so proportioned that the distanceacross any one of the wedges at the line of demarcation is substantiallythe same for the metal having the same carbide balance. In other'words,the constitution of the iron as measured by the wedge test is the sameregardless of the particular size of standardized The distancedemarcation between the white and the gray iron is sometimes referred toas the constitutional carbide wedge values, or more preferably asconstitutional wedge values. The line of demarcation between the whiteand the gray iron as measured by the wedge test is also-a measure-' mentor indication ofthe sensitivity tochilling from the molten condition. i

across direct ratio to the be made.

bonlzation values of the mixture,

graphltisedtoai'swedseshowthefollowing physical properties when pouredinto %.-inch secpoured with the graphibeing designated as "Iron No. A"and the section being poured with the graphitised "B" mixture beingdesignated as Iron No.

' ma No. B 47,850 tensile (a. s. i.)

graphitizing agents with the molmetal as it flows from the cupola or inthe prior to the time the molten metal into the molds. The graphitizedmetal into a casting of wedge form shows diiferent line of demarcationbetween white iron and the gray iron, in that the is shifted toward theknife when a mixture is said it means that the line of demarcation isterms, referred to as a it; wedge. Technically, the distanceacross theface of the wedge at the new line of demarcation is referred to carbidewedge value or processed as distinguished from constitutional Thedistance at the new line of the processed wedge value is a indication ofthe sensitivity to molten condition and bears a thickness of the castingto It is to be noted that the ratio of the constitutional wedge to theprocessed wedge (M in the A iron is in the ratio of ate 1 while theratio of the constitutional wedge 9b) to the processed wedge (95 in the3" ironisintheratioofiltol.

It has been found that when the ratio of constitutional wedge to theprocessed wedge is greater than 2.0 to 1, the physical properties of theresultant metal when poured in any section casting is always greaterthan 2.0 to 1; and that the physical properties of the metal arepredicated on the relationship-existing between the constitution of themelt recarand graphitizawedge value wedge value. demarcation ormeamrement or chilling from the tion related to sections poured.

This is due to the factors in solidification wherein a higher quantityof primary austenite is formed before eutectic composition is reachedresulting in a finer dendritic pattern.- This factor controls the latentheat value in solidification, and irons made by the methods establishedherein result in iron-solidifying at a substantially higher rate thanthat of ordinary cast iron, thus insuringg'a finer dendritic pattern anda deeper depth of solidity penetrating power.

Thus,.by the process of controlling the quantity of primary austeniteduring the process of solidific'ation and decomposing the resultingcementite formed at the main solidus point, we have, therefore,increased the speed of solidification and refined the crystal grain tosuch an extent that we are able to balance structure solidity andphysical properties in such been considered impossible.

As the specification of castings decrease in properties, the rate ofrecarbonizatlon may also decrease and the ratio of constitutional wedgeto the process wedge values may also decrease; however, for the purposeof solidi y. density and correct crystal structure in conjoining theface of the wedge at the.

'ti ofaninchandiain,2

than when the ratio is less a manner as has hitherto asraess sections.the ratios established later in this specification maybe used.

Inasmuch as the determination of the constitution of the metal may beobtained by the wedge method, we have found that there is a directrelation between the constitiition of the metal and the section to bemade, and that there is a minimum value necessary in each casting toassure a uniformly solid section, The proper constitution of the metalhaving been obtained, the next step is to insure the properdecomposition to eliminate the free cementite which serves no otherpurpose than that of establishing a certain minimum latent heat valuethus causing the molten iron to pass condition in a minimum criticalperiod of time. It must be pointed out that each step in this inventionhas a definite relation to the other and differs only according to theoriginal constitution established as necessary for uniform solidity in agiven thickness or design of casting. The following table isrepresentative for two irons of different constitutional value:

ers to a processed carbide value approximately as follows:

Pr carbide values 40 T 0 Mn Resultant ype Much tensile 1-inch 2-inch3-inch (In) N0 95 it tar- A 48000 s a s a pprox. N0. 2 9t: 96: 962-36:Approx. 4 .000

- operator desires to pour a The values given above are typicalrelations as will assure dense, solid, fine grained castings of definitephysical properties which are fully machinable and having an allpearlitic structure.

It is to be observed that for a certain section to be made, apre-determined process wedge valu as measured by the remaining carbideat the tip of the wedge is required, and we find, for machinablecastings, that, the processed wedge value should not substantiallyexceed, as a maximum limit, a value greater than one-third the thicknessof the casting to be made; and should not be substantially below, as aminimum limit, a. value less than one-tenth of the thickness of thecasting to be made for sections up to substantially one and one-halfinch thick, and less than one-twelfth of the thickness of the castingtobe made for sections ranging from substantially one and one-half inchthick to substantially four inches thick, and less than one-sixteenth ofthe thickness of the castings to he made for sections more thansubstantially four inches thick.

In explaining the above table of figures, let it be assumed in theoperation of a foundry that the section or a casting one inch thickhaving a resultant tensile strength of approximately forty-eightthousand pounds p. s. i. The first step is to charge the cupola with amixture having a recarbonization value ranging from from the liquid tothe solid asmess 2.50% to 1.50% which gives a constitutional carbidevalueof substantially "la. In practice, this range of recarbonizationvalun is preferably obtained by employing 60% to 80% steel mix. Afterthe constitutional carbide value of "In is the maximum titheconstitutional carbide wedge maximum obtained, the next step is tographitize the molten metal as it ilows from the cupola or in the ladle.

to the processed carbide'value of substantially "/u.

By maintaining the constitutional carbide value by redarbonisation andthe processed carbide value by mphitis ation as set forth in this ex-,ample, the iron when molded into a one-inch section would have aresultant tensile strength. oi approximately forty-eight thousand poundsp. s. i.

when pouring uncommonly the foundry, the correct constitutional carbidevalues are sometimes obtained by raising, the recarbonisatlon valuehigher than given in the table above. As an illustration, it isnecessary to have a When value of 2.50% to 3.00% when dealing withsections of 12 inches and up.

Although we have described our invention with heavy sections in valuesbeing less;than two and one-half the processed carbide wedgevalueshereinabovedefined,

3. The method of making cast iron castings, comprising the selection ofa mixture of ferrous materials of .a recarbonization value ofsubstantially 1.50% to 0.50%, melting this mixture to give aconstitutional carbide wedge value embraced in a range having a minimumvalue of at least substantially for castings substantially one inchthick ih ior castings substantially two inches thick, for castingssubstantially three inches thick, and tially fourinchis thick orthicker, and graphitizing the moltennietal to a processed carbide wedgevalues not greater.v

of the casting to a certain degree of particularity. itis understoodthat the present disclosure has been made only by way of example andthat numerous changes in the details of the process, modification in thesteps,

undertaken, variations in the materials used,- and diil'erent values ofwedges establishing carbide balance, may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed. We claim as our invention: Y l. A process for making cast ironcastings, comprising selecting and melting a mixture/"ct ferrousmaterials to give a constitutional calrbi'de wedge value embraced withina range having a minimum value of more than one-sixth the averagesection of the casting to be made and a maximum value of less than twoand one-half times the maximum processed carbide wedge valueshereinafter specified, and graphitizing the molten inetal to a processedcarbide wedge value embraced within a range which bears a direct ratioto the thickness of the casting to -be made, said ratio at minimumvalues of said processedcdrbide range being greater than one to ten forcastings up to substantially one and one-half inches thick, and beinggreater than one to twelve for castings ranging from substantially oneand onehalf inches to substantially iour inches thick, and greater thanone to sixteen for castings more than Esubstantially four inches thick,said 'tratio at maximum values oi the said processed carbide range tothe thickness of thecasting to be, made being not greater than one tothree.

of at least substantially is; for castings substansubsti intially'. fourvalues being less than two and one-half times .the

maximum processed carbide .wedge value-Shere inabove defined.

4. The method of making castiron castings,.-

comprising the melting of selected mixtures or ferrous materials to givea constitutional carbide mum values substantially %z-f r castings ofsubstantially one inch thick, %2, for castings substantially two inchesthick, for castings substantially three inches thick, and to %z forcastings substantially four inches thick or thicker, and graphitizingthe molten'metal to a values of said processed greater than one to tenfor castings up to sub- 11- on to sixteen for j 2. The method of makingcast iron castings, comprising the selection of a mixture of ferrousmaterials of a recarbonization value of substantially 2.50% to 1.50%,melting this mixture to give a constitutional carbide wedge valueembraced in a range having a minimum value of at least substantially forcastings substantially one inch thick, for castings substantially twoinches thick, for castings substantially three inches thick, and to forcastings substantially four inches thick or thicker, and graphitizingthe molten metal toa processed carbide wedge value embraced in a rangehaving maximum values not greater than one-third the thickness of thecasting to be'made and minimum processed carbide wedge value embracedwithin aQi-jrange which bears a direct ratio to the thickness of thecasting to be made, said ratio at minimum carbide range being stantiallyone and one half inch thick, and being greater than 'one to twelviorcastings ranging from substantially one ando'ne-half inches tosubstantially four inches thick, and greater than tially'four inchesthick, said ratio at maximum values of the said'processed carbide rangeto the thickness of the casting tone made being not greater than one tothree, the maximum of the constitutional carbide range values being lessthan two and one half ti'ines the maximum processed carbide wedge valueshereinabove specified; 51A process for making cast iron castings,comprising selecting and melting a mixture of ferrous material to give aconstitutional carbide wedge value embraced within a range havingaminimum value oi more than one-sixth the avervalues of at leastsubstantially for castings" substantially one inch thick, 'for-castingssubstantially two inches thick, lt for castings sub- -'-..stantiallythree inches thick and to- %2 for castings substantially four inchesthick or thicker,

ge secticn of the casting to be made and a aximum value of less than twoand one-half times the maximum processed carbide wedge valueshereinafter specified, and graphitizlng the molten metal to a processedcarbide wedge value embraced within a range which bears a direct ratioto the thickness of the casting to be made, said ratio atminimum valuesof said processed carbide range being greater than one to ten forcastings up to substantially one and one-half inches thick; said ratioat ,maxirnum values ofthe said processed carbide range to the thicknessof the castings to be made being not greater than one to three.

=95, to for castings substan' ches thick or thicker, the a. maximum orthe constitutional carbide range castings more than substanbe made, saidratio at ness of the casting to be made being not 6. A process formaking cast iron castings, comprising selecting and melting a mixture orferrous materials to give a constitutional carbide] wedge value embracedwithin a range having a minimum value of more than one-sixth the averagesection of the casting to be made and a maximum value of less than twoand one-half 9. A process to give positive control of physicalproperties in.-a ferrous casting, comtimes the maximum processed carbidewedge values hereinafter specified. and graphltizing the molten metal toa processed carbide wedge value embraced within a range which bears adirect ratio to the thickness of the casting to be made,

' three.

7. A process for making cast iron casting comprising selecting --andmelting a mixture of ferrous materials to give a constitutional carbidewedge value embraced within a range having a minimum value of more thanone-sixth the average section of the casting to be made and a maximumvalue of less than two and one-half times the maximum processed carbidewedge values hereinafter specified, and graphitizing the molten metal toa processed carbide wedge value embraced within a range which bears adirect ratio to the thickness of the casting to minimum values of saidprocessed carbide range being greater than one to sixteen for castingsmore than substantially four inches thick, said ratio at maximum valuesof the said processed carbide range to the thickgreater than one tothree.

8. A process to give positive control ofthe physical properties in aferrous casting, comprising'selecting and melting a mixture of ferrousmaterials whereby the molten material, when cast in a standard wedgetestpiece as described in the specification, and then broken in two,exhibits upon the broken faces both grey and white iron with a line ofdemarcation therebetween of such a length as to be embraced within arange having a minimum value of more than one sixth the average sectionof the castings to be made, and graphitizing, the molten materialwhereby the graphitized molten material, when cast in a standard wedgetest piece as described in the specification, and then broken in two,exhibits upon the broken faces a larger amount of grey iron and asmaller amount of white iron with a new and shorter line of demarcationthan that exhibited on the first mentioned test piece, said new line ofdemarcation being of such length as to be embraced within a range whichbears a direct ratio to the thickness of the casting to be made, saidratio at minimum values of the range for the new line of demarcationbeing greater than one to ten for castings up to substantially one andone-half inches thick, said ratio at maximum values of the range, forthe new line of demarcation to the thickness of the castings to be madebeing not greater than one to three. the maximum value of the range forthe first mentioned line of demarcation being less than two and one-halftimes the maximum length of the second line of demarcation.

hibits upon the prising selecting andmelting a mixture of ferrousmaterials whereby the molten material. when cast in a standardwedge-test piece as described in the specification, and then broken inexhibits upon the broken races both grey and white iron with a line ofdemarcation therebetween of such a length as to be embraced within arange having a minimum value of more than one sixth the average sectionof the castings to be made, and graphitizing the molten material wherebythe graphitized molten material, when cast in a standard wedge testpiece as described in the specification, and then broken in two. ex-

broken faces a larger amount of when and a smaller amount of white ironwith a new and shorter line of demarcation than that exhibited on thefirst mentioned test piece, said new line of demarcation being of such a.lengthastobeembracedwithinaransewhich bears a direct ratio to thethickness of the casting to be made, said ratio at minimumvalues of therange for the new line of demarcation being greater than one to twelvefor the castings ranging from substantially one and onehalf'inches tosubstantially four inches thick. said ratio at maximum values of therange for the new line of demarcation to the thickness of the castingsto be made being not greater than one to three. the maximum value of theran for the first mentioned line of demarcation being less than two andone-half times the maximum length of the second line of demarcation.

10. A process to give positive control of the physical properties in aferrous castin comprising selecting and melting a mixture of ferrousmaterials whereby the molten material.

when cast in a standard wedge test piece as described in thespecification, and then broken in two, exhibits upon the broken facesboth grey and white iron with a line of demarcation therebetween of sucha length as to be embraced within a range having a minimum value of morethan one sixth the average section of the castings to be made, andgraphitizing the molten material whereby the graphitiaed moltenmaterial, when cast in a standard wedge test piece as described in thespecification, and then broken in two, exhibits upon the broken faces alarger amount of grey iron and a smaller amount of white iron with a newand shorter line of demarcation than that exhibited on the firstmentioned test piece, saidnew line of demarcation being of such a lengthas to be embraced within a range which bears a direct ratio to thethickness of the castingto be made, said ratio at minimum values of therange for the new line of demarcation being greater than one to sixteenfor castings more than substantially four inches thick, said ratio atmaximum values of the range for the new line of demarcation to thethickness of the castings to be made being not greater than one tothree, the maximum value of the range for the first mentioned line ofdemarcation being less than two and one-half times the giaximum lengthof the second line of demarcaon. OHVER SMAILEY.

HERBERT A. REECE.

